Die cushion



Oct. 13, 1964 D. H. GARDNER DIE CUSHION 2 Sheets-Sheet 1 Filed 001;. 10, 1961 INVENTOR. DONALD HENRY GARDNER jwhw 5 0M. 34 m ATTORNEY Oct. 13, 1964 D. H. GARDNER 3,

DIE CUSHION Filed Oct. 10. 1961 2 Sheets-Sheet 2 7 ses 4/ IN V EN TOR. DONALD HENRY GARDNER fly/L7 BY A TTORNEV United States Patent 3,152,565 DIE CUSHION Donald Henry Gardner, Cranston, R.I., assignor to Elastic Die Engineering Company, Warwick, R.I., a corporation of Rhode Island Filed Oct. 10, 1961, Ser. No. 144,255 Claims. (Cl. 113-46) This invention relates to punch and die sets and more particularly to an improvement in the die cushion.

This application is a continuation-in-part of United States application Serial #137,290, filed September 11, 1961.

A punch and die set is an assembly consisting of an upper member called the punch holder and a lower member called the die holder. The under surface of the punch holder and the top surface of the die holder are those on which the punch and die sections of a punch press tool are mounted. In use the die holder is clamped to the bed of a punch press, while the upwardly extending punch holder shank is fastened in the clamping orifice provided in the reciprocating punch press ram. The punch is actuated by the reciprocating motion of the ram. Mating guide posts and bushings of an assembled die set assist in maintaining punch and die set alignment during the operation of the punch press.

The present invention is directed to punch and die sets in which the die holder is associated with a movable pressure ring. In the past there have been many different types of movable pressure rings. For example, United States Patent #1,475,437 is directed to a spring resistant pressure ring, which enables the pressure ring resistance to be readily, precisely and extensively varied. In United States Patent 1,556,611 the movable pressure ring is provided with fluid pressure resistance in the form of a vacuum. This was declared to be an improvement over other hydraulic fluid pressure resistant pressure rings. In United States Patent #1,606,141 electro-magnetic means is employed upon the pressure ring so it can grip the work piece and hold it with the desired degree of pressure. And in United States Patent #1,561,770 a cam connected to the pressure ring is oscillated from a rotating part of the press. This connection is effected directly or through a resilient buffer associated with the pressure ring. It is evident that problems have always existed in movable pressure ring die holders because so many different types of mechanisms have been employed to solve the problems.

Movable pressure rings are employed in die sets to permit metal blanks to be shaped and drawn and at the same time prevent the margin of a metal blank from wrinkling or cracking while it is being drawn or shaped.

Past movable pressure ring devices limited the drawing operation to between twenty-five and thirty percent of the diameter of the metal or work blank. That is, a three inch diameter work blank struck by a one and one half inch diameter punch permitted a draw of approximately three eighths of an inch. If a deeper draw was needed, two additional successive draw operations would be required to produce a three quarter inch draw.

It is therefore an object of the present invention to provide a die cushion or movable pressure ring with a construction which will provide a minimum of a fifty percent draw in a single punch press operation while eliminating wrinkling or cracking in the blank.

Another object of the present invention is to provide a die cushion which will accurately transfer the minutest detail of design from a punch to a work blank.

It is still another object of the present invention to provide an inexpensive die cushion which draws and shapes metal blanks with a greater degree of accuracy than was heretofore known.

A further object of the present invention is to provide a die cushion which reduces the number of operations required to produce a given depth of deep draw and which does not change the gage of the blank in the drawing and shaping operation.

And still another object of the present invention is to provide means for adjusting and/or varying the resistance of the element which offers resistance to the movable pressure ring or pad.

Other objects of the present invention will become apparent in part and be pointed out in part in the following specification and claims.

Referring to the drawings in which similar characters of reference indicate corresponding parts in all the figures:

FIGURE 1 is a perspective view of a punch and die set embodying the present invention.

FIGURE 2 is a perspective view of the punch holder.

FIGURE 3 is a perspective view of the movable pressure pad.

FIGURE 4 is a perspective view of the die holder.

FIGURE 5 is a vertical sectional view taken on line 5-5 of FIGURE 1.

FIGURE 6 is a vertical sectional view taken on line 6-6 of FIGURE 2 showing the form of die cushion illustrated in FIGURE 9.

FIGURE 7 is a perspective view in detail of the form of die cushion illustrated in FIGURES 1, 2 and 5.

FIGURE 8 is a modified form of die cushion.

FIGURE 9 is another form of die cushion.

FIGURE 10 is still another form of die cushion.

FIGURE 11 is still another modified form of die cushion.

FIGURE 12 is a view similar to FIGURE 5 illustrating the position within the punch holder of the form of die cushion illustrated in FIGURE 11.

FIGURE 13 is a view similar to FIGURE 5 showing the die cushions compressed.

In proceeding with this invention, reference numeral 10, generally designates the new and improved punch and die set.

The punch holder, generally indicated by reference numeral 12, consists preferably of a solid block of steel, formed to provide a block body 9 having a base 13 and two oppositely and parallel located inner walls 14, 15 respectively. Inner wall 14 is integrally formed with end walls 16, 17. Inner wall 15 is integrally formed with end walls 18, 19. Base 13 is recessed to provide a seat 21 adapted to accommodate a plate 22 having a wall 23 which forms a chamber 24 in combination with end walls 16, 17 and inner wall 14. Similarly, base 13 is recessed to provide a second seat 25 adapted to accommodate a plate 26 having a wall 27 which forms a chamber 28 in combination with inner wall 15 and end walls 18, 19. Plate 22 is welded or otherwise secured to end walls 16, 17 and base 13. Plate 26 is welded or otherwise secured to end walls 18, 19 and base 13.

A punch 30 is fixed in block body 9. A plurality of conventional die posts, illustrated as two in number 31, 32 are secured in base 13.

In effect, punch holder 12 comprises a block of steel provided with a plurality of chambers, illustrated as two in number 24, 28, for purposes which will presently appear. The block 12 forms the lower or punch holding section of a die set.

The pressure pad, generally indicated by reference numeral 40, consists of a plate 41 having a plurality of conventional die bushings, illustrated as. two in number 42, 43, adapted to slidingly engage die posts 31, 32, respectively. Plate 41 is provided with two oppositely and parallel located slots 44, 45 adapted to be aligned with chambers 24, 28, respectively, when die bushings 42, 43 slidingly engage die posts 31, 32, respectively.

A plurality of die cushion plates, illustrated as four in number, 46, 47, 48 and 49 are removably secured in slot 44 by means of dowel pins 50 which pass through orifices provided in plate 41 and in said die cushion plates. Similarly, die cushion plates 51, 52, 53, 54 are removably secured in slot 45 by means of dowel pins 55 which pass through orifices provided in plate 41 and in said last mentioned die cushion plates.

Die cushion plates 46, 47, 48, 49 are adapted to freely reciprocate in chamber 24. Die cushion plates 51, 52, 53, 54 are adapted to freely reciprocate in chamber 28.

As illustrated in FIGURES 2, 5 and 7 the die cushions 60 may take the form of elongated cylindrical strips.

The factor common to all of the different forms of die cushions illustrated in FIGURES 7, 8, 9, 10 and 11 is that they are fabricated from a material having the physical characteristics of uniform expansion and uniform contraction. A durometer reading of ninety-five (95) but not less than seventy (70). An elongation potential of approximately six hundred fifty percent (650%) but not less than five hundred percent (500% A normal elongation of two hundred percent at eighteen hundred pounds per square inch pulling force. A minimum tensile strength of forty-three hundred pounds per square inch. One such material is a polyurethane, commercially known as Elasta Cast.

A plurality of die cushions 60 are located in chambers 24 and 28. Die cushion plates 46, 47, 48, 49 and 51, 52, 53, 54 will engage the tops of die cushions 60. When pressure pad is caused to move up and down in a conventional die press action, die cushions 60 will olfer uniform resistance to the die cushion plates. If this resistance is too great, then dowel pins or 55 may be removed so as to render one or more of the die cushion plates inoperative. In this manner pressure pad 40 may be opposed by eight die cushion plates, as illustrated in FIGURES 1, 2 and 3, or with fewer than eight die cushion plates.

Another way the die cushion resistance to the die cushion plates may be varied is illustrated in FIGURE 8 wherein the elongated cylindrical strips A may be provided with an axial bore 61A. The removal of material axially causes the die cushions 60A to ofier less resistance than when such material is not removed, as illustrated in FIGURE 7.

The die cushion may take any one of the forms illustrated in FIGURES 9, 10 and 11. The different geometric shapes cause the die cushions to vary in resistance from one shape to the other shape. The modified forms of die cushions shown in FIGURES 9, 10 and 11 allow a greater length of stroke for die block 70 than the length of stroke permitted by die cushion 60. The resistance offered by each modified form of die cushion will be different one from the other.

Referring to FIGURES 1, 2, 3 and 4, plate 41 is provided with a punch orifice 65 adapted to slidingly engage punch 30. A punch plate 66 provided with a selected contour 67 is secured to plate 41 by means of dowels 68 and screws 69. A die block 70 is provided with a shank 71, a contour 72 to mate with contour 67 and a die 73 adapted to matingly engage punch 30. Shank 71 is held in a press in a manner known to the art. Die block 70 is also provided with a shoulder and a bottom 74.

A work piece or sheet metal blank (not shown) having the peripheral contour of contour 67 will be placed within contour 67 and over the top of punch 30 which will be level with the top of plate 41. The reciprocating ram of a press (not shown) housing shank 71 will cause die 70 to move toward and away from pressure pad 40. In this reciprocating movement contour 72 will matingly or slidingly engage contour 67. The bottom 74 will engage blank and through said engagement force plate 41 downward so as to force punch 30 into die 73, thereby forming the blank to the shape of punch 30 and die 73. The downward movement of plate 41 will be guided by die posts 31,

32 slidingly engaging die bushings 42, 43, respectively. The downward movement of plate 41 will be constantly and uniformly resisted by die cushions 60 or 60A as the die cushions are engaged by die cushion plates 46, 47, 48, 49 and 51, 52, 53, 54. It is this uniform and constant opposing pressure which allows the metal of the blank to be formed by sliding or flowing evenly over the punch 30 and around the die 73 without reducing the thickness of the blank and without wrinkling or cracking of the blank. If the downward pressure of the die block 70 and die 73 is uneven or if the pressure opposing the die block 70 varies by increasing or decreasing, then the metal blank will snag. The punch 30 will wrinkle or rupture the metal blank.

The die cushion plates 51, 52, 53, 54, 46, 47, 48, 49 may be removed singularly from slot 45 or 44 respectively, by removing the dowel pins 55, 50, respectively, so as to vary the resistance of the die cushions 60, 60A, etc., against pressure pad 40 and die 70. A given thickness of blank or shape of blank will require a diiferent resistance. The dilferent geometric shapes of the various die cushions 60, 60A, etc., also provides a means of varying the resistance of the die cushions.

Having shown and described preferred embodiments of the present invention by way of example, it should be realized that structural changes could be made and other examples given without departing from either the spirit or scope of this invention.

What I claim is:

l. A punch and die set comprising a punch holder consisting of a block fabricated from steel and provided with a plurality of chambers, a plurality of die posts fixed in said steel block, a punch fixed in said block, a pressure pad provided with a plurality of die bushings adapted to slidingly engage said plurality of die posts, and a punch orifice, a punch plate, provided with a preselected contour, fixed to said pressure pad, a die block having a shank, a contour adapted to matingly engage said preselected contour, a die adapted to matingly engage said punch, die cushion means located in said plurality of chambers, said die cushion means fabricated from a polyurethane material having the physical characteristics of a durometer reading of approximately ninety-five, an elongation potential of approximately six hundred percent, a normal elongation of approximately two hundred percent at eighteen hundred pounds per square inch and a tensile strength of approximately forty-three hundred pounds per square inch, die cushion plate means on said pressure pad engaging said die cushion means and means on said die block engaging said pressure pad whereby relative movement of said die block toward said punch plate matingly engages said die block contour with said preselected contour and said die with said punch, said punch passing through said punch orifice, said die cushion means uniformly resisting the engagement of said die with said punch.

2. A punch and die set comprising a punch holder consisting of a block fabricated from steel and provided with two opposite and parallel chambers, two die posts fixed in said steel block, a punch fixed in said block, a pressure pad provided with two die bushings adapted to slidingly engage said two die posts, and a punch orifice, a punch plate, provided with a preselected contour fixed to said pressure pad, a die block having a shank, a contour adapted to matingly engage said preselected contour, a die adapted to matingly engage said punch, die cushion means located in said two opposite and parallel chambers, said die cushion means fabricated from a polyurethane material having the physical characteristics of a durometer reading of approximately ninety-five, an elongation potential of approximately six hundred percent, a normal elongation of approximately two hundred percent at eighteen hundred pounds per square inch and a tensile strength of approximately forty-three hundred pounds per square inch, die cushion plate means on said pressure pad engaging said die cushion means and means on said die block engaging said pressure pad whereby relative movement of said die block toward said punch plate matingly engages said die block contour with said preselected contour and said die with said punch, said punch passing through said punch orifice, said die cushion means uniformly resisting the engagement of said die with said punch.

3. A punch and die set comprising a punch holder consisting of a block fabricated from steel and provided with a base and a plurality of chambers, two die posts fixed in said base, a punch fixed in said block, a pressure pad provided with two die bushings adapted to slidingly engage said two die posts, and a punch orifice, a punch plate, provided with a preselected contour, fixed to said pressure pad, a die block having a shank, a contour adapted to matingly engage said preselected contour, a die adapted to matingly engage said punch, a plurality of elongated die cushions located in said plurality of chambers, said die cushions fabricated from a polyurethane material having the physical characteristics of a durometer reading of approximately ninety-five, an elongation potential of approximately six hundred percent, a normal elongation of approximately two hundred percent at eighteen hundred pounds per square inch and a tensile strength of approximately forty-three hundred pounds per square inch, a plurality of die cushion plate means removably securing said die cushion plate to said pressure pad, and means on said die block engaging said pressure pad whereby relative movement of said die block toward said punch plate matingly engages said die block contour with said preselected contour and said die with said punch, said punch passing through said punch orifice, said plurality of die cushion plates engaging said die cushions, said die cushions uniformly resisting the engagement of said die with said punch through said die cushion plates.

4. A punch and die set comprising a punch holder consisting of a block fabricated from steel and provided with a base and two opposite and parallel chambers, two die posts fixed in said base, a punch fixed in said block, a pressure pad provided with two die bushings adapted to slidingly engage said two die posts, and a punch orifice, a punch plate, provided with a preselected contour, fixed to said pressure pad, a die block having a shank, a contour adapted to matingly engage said preselected contour, a die adapted to matingly engage said punch, a plurality of elongated tubular strips forming die cushions located in said two opposite and parallel chambers, said elongated tubular strips being fabricated from a polyurethane material having the physical characteristics of a durometer reading of approximately ninety-five, an elongation potential oi approximately six hundred percent, a normal elongation of approximately two hundred percent at eighteen hundred pounds per square inch and a tensile per square inch, a plurality of die cushion plate means removably securing said die cushion plates to opposite sides of said pressure pad, and means on said die block engaging said pressure pad whereby relative movement of said die block toward said punch plate matingly engages said die block contour with said preselected contour and said die with said punch, said punch passing through said punch orifice, said plurality of elongated tubular strips uniformly resisting the engagement of said die with said punch through said die cushion plates.

5. A punch and die set comprising a punch holder consisting of .a steel block provided with opposite and parallel located chambers, a plurality of die posts fixed in said steel block, a punch secured in said steel block, a pressure pad provided with a plurality of die bushings adapted to slidingly engage said plurality of die posts, opposite and parallel located slots in said pressure pad aligned with said opposite and parallel located chambers and an orifice, a plurality of die cushion plates removably secured in said slots and projecting into said chambers, a punch plate provided with a preselected contour secured to said pressure pad, a die block having a shank, a contour adapted to slidingly engage said preselected contour, a die adapted to slidingly engage said punch, and a bottom, a plurality of die cushions housed in said chambers and engaged by said plurality of die cushion plates, said die cushions fabricated from a polyurethane material having the physical characteristics of a durometer reading of approximately ninety-five, an elongation potential of approximately six hundred percent, a normal elongation of approximately two hundred percent at eighteen hundred pounds per square inch and a tensile strength of approximately forty-three hundred pounds per square inch, whereby relative movement of said die block toward said punch plate matingly engages said bottom with said punch plate and said die block contour with said preselected contour and said die with said punch, said punch passing through said contour, said bottom forcing said punch plate and pressure pad into a work stroke whereby said die cushion plates engage said plurality of die cushions, said plurality of die cushions uniformly resisting engagement of said die with said punch.

References Cited in the file of this patent UNITED STATES PATENTS 1,527,266 Nathanson et al. Feb. 24, 1925 2,321,075 Frey et al. June 8, 1943 2,400,004 lager May 7, 1946 FOREIGN PATENTS 938,306 Germany Jan. 26, 1956 127,761 Great Britain June 12, 1919 

1. A PUNCH AND DIE SET COMPRISING A PUNCH HOLDER CONSISTING OF A BLOCK FABRICATED FROM STEEL AND PROVIDED WITH A PLURALITY OF CHAMBERS, A PLURALITY OF DIE POSTS FIXED IN SAID STEEL BLOCK, A PUNCH FIXED IN SAID BLOCK, A PRESSURE PAD PROVIDED WITH A PLURALITY OF DIE BUSHINGS ADAPTED TO SLIDINGLY ENGAGE SAID PLURALITY OF DIE POSTS, AND A PUNCH ORIFICE, A PUNCH PLATE, PROVIDED WITH A PRESELECTED CONTOUR, FIXED TO SAID PRESSURE PAD, A DIE BLOCK HAVING A SHANK, A CONTOUR ADAPTED TO MATINGLY ENGAGE SAID PRESELECTED CONTOUR, A DIE ADAPTED TO MATINGLY ENGAGE SAID PUNCH, DIE CUSHION MEANS LOCATED IN SAID PLURALITY OF CHAMBERS, SAID DIE CUSHION MEANS FABRICATED FROM A POLYURETHANE MATERIAL HAVING THE PHYSICAL CHARACTERISTICS OF A DUROMETER READING OF APPROXIMATELY NINETY-FIVE, AN ELONGATION POTENTIAL OF APPROXIMATELY SIX HUNDRED PERCENT, A NORMAL ELONGATION OF APPROXIMATELY TWO HUNDRED PERCENT AT EIGHTEEN HUNDRED POUNDS PER SQUARE INCH AND A TENSILE STRENGTH OF APPROXIMATELY FORTY-THREE HUNDRED POUNDS PER SQUARE INCH, DIE CUSHION PLATE MEANS ON SAID PRESSURE PAD ENGAGING SAID DIE CUSHION MEANS AND MEANS ON SAID DIE BLOCK ENGAGING SAID PRESSURE PAD WHEREBY RELATIVE MOVEMENT OF SAID DIE BLOCK TOWARD SAID PUNCH PLATE MATINGLY ENGAGES SAID DIE BLOCK CONTOUR WITH SAID PRESELECTED CONTOUR AND SAID DIE WITH SAID PUNCH, SAID PUNCH PASSING THROUGH SAID PUNCH ORIFICE, SAID DIE CUSHION MEANS UNIFORMLY RESISTING THE ENGAGEMENT OF SAID DIE WITH SAID PUNCH. 